Ubuntu 18.04 / OpenSSH 7.6 support

[pookey]

Ubuntu 18.04 version/build of SSH no longer supports hmac-ripemd160

Release notes for OpenSSH 7.6: https://www.openssh.com/txt/release-7.6

• ssh(1)/sshd(8): remove support for the hmac-ripemd160 MAC.

This is perhaps further weight on the discussion on #45

[rohanaceres]

Any updates in this matter?

[chris-rock]

We are currently looking for new core maintainers for this module. PRs are welcome to bring this module forward!